JP2001313161A - Heating device, picture treating device and picture forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve such a problem that, in the case of using thick paper or 0HT as a recording material, in order to obtain the prescribed gloss and transparency, longer heating and fixing period is necessary, therefore, time for holding and transfer is extended and printing frequency per minute is lowered. SOLUTION: The device has an electromagnetic induction heating member generating heat by the magnetic field generated by a magnetic field generating member, and the rotatable first pressurizing member forming a nip where the first pressurizing member contacts the electromagnetic heating member with pressure, hereupon, the electromagnetic heating member is a looped belt, and the rotatable second pressurizing member is installed at the opposing position to the first pressurizing member which is installed inside the looped belt, and the plane contacting with the second pressurizing member is arranged so that it become parallel to the looped belt at the part where the second pressurizing member and the looped belt contact each other.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a belt heating type heating device and an image forming apparatus such as an electrophotographic apparatus and an electrostatic recording apparatus having the heating device as an image heating device.

[0002]

2. Description of the Related Art An image heating device (fixing device) will be described below as an example of a heating device provided in an image forming apparatus such as a copying machine or a printer to heat and fix a toner image on a recording material.

A recording material (transfer material sheet, electrofax sheet, electrostatic recording paper, 0HP sheet, printing) by an appropriate image forming process means (image forming apparatus) such as an electrophotographic process, an electrostatic recording process, and a magnetic recording process. Paper
A heat roller method is used as a fixing device for heating and fixing an unfixed image (toner image) of target image information formed and carried on a transfer paper or a direct paper on a format paper as a permanent fixed image on a recording material surface. However, recently, a belt heating type device has been put into practical use from the viewpoint of quick start and energy saving. Also, an electromagnetic induction heating system has been proposed.

A) Heat roller type fixing device This fixing device basically has a pressure roller pair of a fixing roller (heating roller) and a pressure roller, and rotates the pressure roller pair to mutually press the pressure roller. A recording material on which an unfixed toner image to be image-fixed is formed and carried is introduced into a fixing nip portion, and the sheet is nipped and conveyed. Is thermally and pressure-fixed to the surface of the recording material.

[0005] The fixing roller generally has a hollow metal roller made of aluminum as a base (core metal), and a halogen lamp as a heat source is inserted and disposed in the inner space thereof. The power supply to the halogen lamp is controlled to control the temperature so that the predetermined fixing temperature is maintained.

In particular, as a fixing device of an image forming apparatus for forming a full-color image in which a capability of sufficiently heating and melting a maximum of four toner image layers to mix colors is required, a core metal of a fixing roller needs to have a high heat capacity. In addition, a rubber elastic layer for wrapping the toner image around the core metal and uniformly melting the toner image is provided, and the toner image is heated via the rubber elastic layer. There is also a configuration in which a heat source is provided in the pressure roller to heat and control the temperature of the pressure roller.

However, this heat roller type fixing device is
Even when the power of the image forming apparatus is turned on and the halogen lamp, which is the heat source of the fixing device, is energized at the same time, even when the heat capacity of the fixing roller is large and the fixing roller and the like are completely cooled, the temperature reaches a predetermined fixing temperature. It takes a considerable waiting time (weight time) to get up and lacks quick start.

Further, it is necessary to supply electricity to the halogen lamp and maintain the fixing roller in a predetermined temperature control state so that the image forming operation can be performed at any time even when the image forming apparatus is in a standby state (non-image output). However, there is a problem that power consumption is large.

In the case of a fixing device having a large heat capacity, such as the fixing device of the above-described full-color image forming apparatus, a delay occurs between the temperature control and the temperature rise of the fixing roller surface. There have been problems such as uneven brightness, uneven gloss and offset.

B) Fixing device of belt heating type This fixing device is disclosed, for example, in JP-A-63-313182, JP-A-2-157788, and JP-A-4-4407.
No. 5, JP-A-4-204980 and the like.

That is, a nip portion is formed by sandwiching a heat-resistant belt (fixing belt) between a ceramic heater as a heating element and a pressing roller as a pressing member. Introduce a recording material on which an unfixed toner image to be fixed is formed and carried between rollers,
By sandwiching and transporting the sheet together with the belt, the heat of the ceramic heater is applied to the recording material via the belt at the nip portion, and the unfixed toner image is thermally pressed onto the recording material surface by the pressing force of the pressure roller. It is to fix it.

This belt heating type fixing device can be constructed as an on-demand type device using a ceramic heater and a member having a low heat capacity as a belt. Therefore, only when the image forming apparatus performs image formation, the ceramic heater as a heat source may be energized so as to generate heat to a predetermined fixing temperature, and from the time when the image forming apparatus is turned on to the state where image formation is executable. This has advantages such as a short waiting time (quick start property) and a significantly low power consumption during standby (power saving). However, a full-color image forming apparatus requiring a large amount of heat or a fixing device for a high-speed model has a calorific point.

C) Electromagnetic induction heating type fixing device For example, Japanese Utility Model Laid-Open Publication No. Sho 51-1099739 discloses an induction heating fixing device in which current is induced in a fixing roller by magnetic flux to generate heat by Joule heat. this is,
By utilizing the generation of the induced current, the fixing roller can directly generate heat, thereby achieving a more efficient fixing process than a heat roller type fixing device using a halogen lamp as a heat source.

However, since the energy of the alternating magnetic flux generated by the exciting coil as the magnetic field generating means is used to raise the temperature of the entire fixing roller, the heat dissipation is large, the density of the fixing energy with respect to the input energy is low, and the efficiency is low. There was a problem.

Therefore, in order to obtain the energy acting on the fixing at a high density, the exciting coil is brought closer to the fixing roller which is a heating element, or the alternating magnetic flux distribution of the exciting coil is concentrated near the fixing nip portion. An efficient fixing device has been proposed.

FIG. 13 shows a schematic configuration of an example of an electromagnetic induction heating type fixing device in which the alternating magnetic flux distribution of the exciting coil is concentrated in the fixing nip portion and the efficiency is improved.
In 3, reference numeral 10 denotes a cylindrical fixing belt having an electromagnetic induction heating layer (a conductor layer, a magnetic layer, and a resistor layer) and serving as a rotating body of electromagnetic induction heating. Reference numeral 16 denotes a belt guide member having a gutter-shaped cross section having a substantially semicircular arc cross section.
Is loosely fitted outside the belt guide member 16.

Numeral 15 denotes a magnetic field generating means disposed inside the belt guide member 16 and comprises an exciting coil 18 and an E-shaped magnetic core (core material) 17. Numeral 30 denotes an elastic pressure roller, which forms a fixing nip portion N having a predetermined width with a predetermined pressing force on the lower surface of the guide member 16 with the fixing belt 10 being interposed therebetween, and mutually pressed.

The magnetic core 17 of the magnetic field generating means 15 has
The fixing nip portion N is disposed at a position corresponding to the fixing nip portion N. The pressing roller 30 is driven to rotate in the counterclockwise direction indicated by the arrow by the driving means M. A rotational force acts on the fixing belt 10 by a frictional force between the pressing roller and the fixing belt 10 due to the rotational driving of the pressing roller 30, and the fixing belt 10 has an inner surface at a fixing nip portion N and a belt guide member. 16 while sliding in close contact with the lower surface of the pressure roller 3 in the clockwise direction indicated by the arrow.
At a peripheral speed substantially corresponding to the rotational peripheral speed of 0, the belt guide member 16 is rotated outside (pressure roller driving method).

The belt guide member 16 has a fixing nip portion N
, And supports the exciting coil 18 and the magnetic core 17 as the magnetic field generating means 15, supports the fixing belt 10, and improves the conveyance stability when the fixing belt 10 rotates. The belt guide member 16 is an insulating member that does not hinder the passage of magnetic flux, and is made of a material that can withstand a high load.

The exciting coil 18 generates an alternating magnetic flux by an alternating current supplied from an exciting circuit (not shown). The alternating magnetic flux is intensively distributed to the fixing nip N by the E-shaped magnetic core 17 corresponding to the position of the fixing nip N, and the alternating magnetic flux is applied to the electromagnetic induction heating layer of the fixing belt 10 at the fixing nip N. Generates eddy currents.

This eddy current generates Joule heat in the electromagnetic induction heating layer due to the specific resistance of the electromagnetic induction heating layer. The electromagnetically induced heat of the fixing belt 10 is concentratedly generated in the fixing nip N where the alternating magnetic flux is intensively distributed, and the fixing nip N is heated with high efficiency. The temperature of the fixing nip portion N is controlled such that a predetermined temperature is maintained by controlling the current supply to the exciting coil 18 by a temperature control system including a temperature detection unit (not shown).

Thus, the pressure roller 30 is driven to rotate,
Accordingly, the cylindrical fixing belt 10 rotates around the belt guide member 16 and moves from the excitation circuit to the excitation coil 18.
As a result of the electromagnetic induction heating of the fixing belt 10 by the power supply to the fixing nip N and the temperature of the fixing nip N rising to a predetermined temperature, the unfixed toner conveyed from the image forming means (not shown) The recording material P on which the image t is formed is introduced between the fixing belt 10 and the pressure roller 30 in the fixing nip portion N with the image surface facing upward, that is, opposed to the fixing belt surface. The image surface comes into close contact with the outer surface of the fixing belt 10, and the fixing nip N is conveyed together with the fixing belt 10.

In the process in which the recording material P is nipped and conveyed through the fixing nip portion N together with the fixing belt 10, the unfixed toner image t on the recording material P is heated by the electromagnetic induction heat of the fixing belt 10. Is fixed on the recording material P by heating. When the recording material P passes through the fixing nip portion N, it is separated from the outer surface of the rotary fixing belt 10 and discharged and conveyed.

[0024]

Since the conventional image heating apparatus (fixing apparatus) as a heating apparatus is constructed as described above, when the recording material is thick paper or OHT, it has a predetermined gloss and light. To obtain transparency, a longer heat fixing time than usual was required. For this reason, since the holding conveyance time in the nip portion of the heating device is delayed, there is a problem that the number of printed sheets per minute is reduced.

The present invention has been made to solve the above-described problems, and a heating apparatus capable of performing sufficient heating even in a short time and realizing a shortened heating time. An object of the present invention is to provide an image heating apparatus and an image forming apparatus that can form a high-quality image by applying a heating apparatus.

[0026]

According to the present invention, there is provided a heating apparatus, an image heating apparatus and an image forming apparatus having the following constitutions.

(1) an electromagnetic induction heating member which generates electromagnetic induction heat under the action of a magnetic field generated by a magnetic field generating means;
A first rotatable pressing member that forms a nip portion by pressing against the electromagnetic induction heating member, and heats the material to be heated passing through the nip portion by the heat generated by the electromagnetic induction heating member. The electromagnetic induction heating member is an endless belt, and has a second pressurizing member rotatable at a position inside the endless belt facing the first pressurizing member.
A heating device characterized in that a plane contacting the second pressing member at a contact point between the pressing member and the endless belt is parallel to the endless belt.

(2) The heating device according to (1), wherein the magnetic field generating means is disposed inside an endless belt.

(3) The heating device according to (2), wherein a means for bringing the heated member into contact with the endless belt is provided upstream of the nip portion in the traveling direction of the heated member.

(4) The heating device according to (1), wherein the magnetic field generating means is provided on the upstream side of the nip portion in the traveling direction of the member to be heated.

(5) The heating device according to (1) to (4), wherein the endless belt temperature detecting means is provided on the endless belt downstream of the magnetic field generating means and upstream of the nip portion.

(6) A heating device according to (1) to (5), wherein a member for rotatably holding the end of the endless belt is provided at the end of the rotatable pressure member inside the endless belt. apparatus.

(7) The width of the endless belt is L _B , the length of the pressing portion of the first pressing member is L _R1 , and the length of the second pressing member that can contact the endless belt is L _B1 . When _{L R2, L B> L R1} > heating apparatus which satisfies the relationship L _R2 characterized by (1) to (6).

(8) An image forming means for forming an image on a recording material, and a heating device according to any one of (1) to (7), wherein the image forming means forms the image on the recording material. An image heating device for subjecting the formed image to heat treatment by the heating device.

(9) An image forming means for forming an image on a recording material, and a heating device according to any of (1) to (8), wherein the image forming means forms the image on the recording material. An image forming apparatus, comprising: the heating device as an image heating device that heats a processed image.

[0036]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) (1) Example of Image Forming Apparatus FIG. 1 is a schematic diagram showing an example of an image forming apparatus to which a heating apparatus according to the present invention is applied. The device is an electrophotographic color printer. In FIG. 1, reference numeral 101 denotes a photoconductor drum (image carrier) made of an organic photoconductor or an amorphous silicon photoconductor, and is driven to rotate counterclockwise as indicated by an arrow at a predetermined process speed (peripheral speed). The photosensitive drum 101 undergoes a uniform charging process of a predetermined polarity and potential by a charging device 102 such as a charging roller during the rotation process.

Next, the laser beam 1 output from the laser optical box (laser scanner) 110 is applied to the charged surface.
At 03, an electrostatic latent image corresponding to the target image information is formed after receiving the scanning exposure processing of the target image information. The laser optical box 110 outputs laser light 103 modulated (on / off) in accordance with a time-series electric digital pixel signal of target image information from an image signal generating device such as an image reading device (not shown). An electrostatic latent image corresponding to target image information scanned and exposed on the surface of the body drum 101 is formed. Reference numeral 109 denotes a laser beam output from the laser optical box 110 to the photosensitive drum 1.
This is a mirror that deflects to the exposure position 01.

In the case of full-color image formation, scanning exposure and latent image formation are performed on a first color-separated component image of a target full-color image, for example, a yellow component image. Is developed as a yellow toner image by the operation of the yellow developing device 104Y. The yellow toner image is transferred to the surface of the intermediate transfer drum 105 at a primary transfer portion T1 which is a contact portion (or a close portion) between the photosensitive drum 101 and the intermediate transfer drum 105. The surface of the rotating photosensitive drum 101 after the transfer of the toner image to the surface of the intermediate transfer drum 105 is the cleaner 1
At 07, cleaning is performed by removing attached residues such as transfer residual toner.

The process cycle of charging, scanning exposure, development, primary transfer, and cleaning as described above performs the second color separation component image (eg, magenta component image,
The magenta developing device 104M is activated), the third color-separated component image (for example, the cyan component image, the cyan developing device 104C is activated), and the fourth color-separated component image (for example, the black component image, the black developing device 104BK is activated). Each color separation component image is sequentially executed, and four toner images of a yellow toner image, a magenta toner image, a cyan toner image, and a black toner image are sequentially transferred onto the surface of the intermediate transfer drum 105 in a superimposed manner. A color toner image corresponding to the image is synthesized and formed.

The intermediate transfer drum 105 is a metal drum 1
05a on the medium resistance elastic layer 105b and the high resistance surface layer 10
5c, is rotated clockwise as indicated by an arrow at substantially the same peripheral speed as the photosensitive drum 101 in contact with or close to the photosensitive drum 101, and a bias potential is applied to the metal drum 105a of the intermediate transfer drum 105. And the toner image of the photosensitive drum 101 is transferred to the surface of the intermediate transfer drum 105 by the potential difference from the photosensitive drum 101.

The color toner image synthesized and formed on the surface of the rotary intermediate transfer drum 105 is transferred to the secondary transfer portion T2, which is a contact nip portion between the rotary intermediate transfer drum 105 and the transfer roller 106, at the secondary transfer portion T2. The image is transferred onto the surface of the recording material P sent from the paper supply unit (not shown) to the transfer unit T2 at a predetermined timing. The transfer roller 106 supplies a charge having a polarity opposite to that of the toner from the rear surface of the recording material P, thereby sequentially transferring the combined color toner images collectively from the surface of the intermediate transfer drum 105 to the recording material P.

The recording material P that has passed through the secondary transfer portion T2 is separated from the surface of the intermediate transfer drum 105, introduced into the image heating device (fixing device) 100 of the present invention, and heat-fixed an unfixed toner image. Then, the sheet is discharged to a discharge tray (not shown) outside the apparatus as a color image formed product. The fixing device 100 will be described in detail in the following section (2).

After the transfer of the color toner image onto the recording material P, the rotating intermediate transfer drum 105 is cleaned by the cleaner 108 by removing the adhered residue such as untransferred toner and paper dust. The cleaner 108 is always kept in a non-contact state with the intermediate transfer drum 105, and during the secondary transfer of the color toner image from the intermediate transfer drum 105 to the recording material P, the intermediate transfer drum 105 is maintained.
Is kept in contact.

The transfer roller 106 is also always kept in a non-contact state with the intermediate transfer drum 105, and during the secondary transfer of the color toner image from the intermediate transfer drum 105 to the recording material P, the intermediate transfer drum 105
Is kept in contact with the recording material P via the recording material P.

The apparatus of this embodiment can also execute a print mode of a monocolor image such as a black and white image. Also, a double-sided image print mode or a multiple image print mode can be executed.
In the case of the double-sided image print mode, the recording material P on which the first-side image has been printed out of the image heating device 100 is turned upside down via a recirculation transport mechanism (not shown), and is again returned to the secondary transfer portion T
2 to receive toner image transfer on two surfaces,
The double-sided image print is output by being again introduced into the image heating device 100 and subjected to the fixing process of the toner image on the two surfaces.

In the case of the multiple image print mode, the recording material P on which the first image has been printed out of the image heating apparatus 100 is printed.
Is transferred to the secondary transfer portion T2 again without being turned upside down via a recirculation transport mechanism (not shown), receives the second transfer of the toner image on the surface on which the first image has been printed, and returns to the image heating device 100 again. The multi-image print is output by being subjected to the second toner image fixing process after being introduced.

(2) Fixing Device (Heating Means) 100 FIG. 2 shows a fixing device 100 using the electromagnetic induction heating method of the present invention.
, FIG. 3 is a front view of the main part, and FIG. 4 is a longitudinal cross-sectional front view of the main part. 2 to 4, reference numeral 10 denotes an endless fixing belt having an electromagnetic induction heating layer (a conductor layer, a magnetic layer, and a resistor layer) and serving as an electromagnetic induction heating rotating body; A semicircular gutter type film guide member, 30 is an elastic pressure roller,
These are the same constituent members and portions as those of the conventional apparatus shown in FIG.

The magnetic field generating means 15 includes the magnetic cores 17a and 17
b and the exciting coil 18. Magnetic core 17a ・ 17
b is a member having a high magnetic permeability, and is preferably a material used for a transformer core, such as ferrite or permalloy, and more preferably a ferrite having a small loss even at 100 kHz or more.

As shown in FIG. 5, an excitation circuit 27 is connected to the power supply sections 18a and 18b of the excitation coil 18. The excitation circuit 27 can generate a high frequency of 20 kHz to 500 kHz by a switching power supply.

The exciting coil 18 generates an alternating magnetic flux by an alternating current (high-frequency current) supplied from the exciting circuit 27. An eddy current flows in the fixing belt 10, which is an electromagnetic induction heating belt, in a direction to cancel the alternating magnetic field, generating Joule heat, and the fixing belt 10 generates heat.

A drive roller 31 and a belt guide member 16 are disposed inside the endless fixing belt 10, and the belt guide member 16 has a substantially semicircular gutter-shaped cross section, and the endless fixing belt 10 Is loosely fitted. The belt guide member 16 holds the magnetic cores 17a and 17b as the magnetic field generating means 15 and the exciting coil 18 inside.

Reference numeral 22 denotes a horizontally long pressing rigid stay provided on the inner surface of the belt guide member 16. 19 is a magnetic core 1
7a, 17b, excitation coil 18 and pressurizing rigid stay 2
It is an insulating member for insulating between the two. Fixing belt 1
The drive roller 31 for rotating 0 is composed of a core metal 31a and a heat-resistant and elastic material layer 31b of silicone rubber, fluoro rubber, fluoro resin, or the like, which is formed and coated concentrically around the core metal in a roller shape. ing. Both ends of the cored bar 31a are rotatably supported and held between sheet metal (not shown) of a chassis of the apparatus.

The drive roller 31 is driven to rotate in a counterclockwise direction indicated by an arrow by drive means (not shown). At both ends of the driving roller 31, flange members 23a and 23b for regulating and holding the end of the fixing belt 10 are rotatably attached to the driving roller 31. The flange members 23a and 23b receive an end of the fixing belt 10 when the fixing belt 10 rotates, and play a role of restricting the shift of the fixing belt along the longitudinal direction.

The core 31a of the drive roller 31 is rotatably fixed to the apparatus chassis 70 by drive roller bearings 29c and 29d. A gear is attached to the cored bar 31a, and the cored bar 31a is driven to rotate in a direction indicated by an arrow by driving means (not shown).

The pressure roller 30 as a pressure member is made of a heat-resistant / elastic material layer such as silicone rubber, fluoro rubber, fluoro resin, etc., which is formed by concentrically forming a roller around the core 30a. 30b, and the core metal 30
Both ends of a are rotatably supported and held between sheet metal (not shown) on the chassis side of the apparatus. If necessary, a release layer such as a fluororesin can be provided on the outermost layer.

Both ends of the pressure roller 30 and the apparatus chassis 7
Pressing springs 25a and 25b are contracted between the 0 side and the spring receiving portions 29a and 29b, respectively, so that a pressing force is applied to the pressing roller 30. In this example, the spring receiving portion 2
Reference numerals 9a and 29b also serve as bearings for the pressure roller 30.
As a result, the lower surface of the driving roller 31 and the upper surface of the pressure roller 30 are pressed against each other with the fixing belt 10 interposed therebetween, thereby forming a fixing nip portion N having a predetermined width.

A rotational force acts on the fixing belt 10 by the frictional force between the driving roller 31 and the inner surface of the fixing belt 10 due to the rotational driving of the driving roller 31, and the fixing belt 10 is driven clockwise as indicated by an arrow. A rotation state is established with a peripheral speed substantially corresponding to the rotational peripheral speed of the rotation.

FIG. 4 shows the longitudinal relationship between the pressing roller 30 and the driving roller 31 with respect to the width of the fixing belt 10. Width L _B of the fixing belt 10, the pressing length L _{R 1} the pressure roller 30, when the contactable length of the fixing belt 10 of the driving roller 31 and _{L R2, L B> L R1} > L R2 It is better to design so as to satisfy the relationship. When the maximum width of the recording material P is L _P , L _R1 ≧ L _P is satisfied. The flange members 23a and 23b are rotatably attached to both ends of the drive roller 31.

In this embodiment, the roller inside the fixing belt 10 is the driving roller 31. However, the driving force may be applied to the pressing roller 30, or both rollers may be applied with the driving force.

FIG. 6 schematically shows how the alternating magnetic flux is generated. FIG. 6A shows a part of the generated alternating magnetic flux C. Alternating magnetic flux C guided to the magnetic cores 17a and 17b
Generates an eddy current in the electromagnetic induction heating layer 1 of the fixing belt 10 between the magnetic core 17a and the magnetic core 17b and between the magnetic core 17a and the magnetic core 17c. This eddy current generates Joule heat (eddy current loss) in the electromagnetic induction heating layer 1 due to the specific resistance of the electromagnetic induction heating layer 1. The heat value Q here is determined by the density of the magnetic flux passing through the electromagnetic induction heating layer 1 and has a distribution as shown in the graph of FIG.

In this graph, the vertical axis indicates the position in the circumferential direction of the fixing belt 10 represented by the angle θ with the center of the magnetic core 17a being 0, and the horizontal axis indicates the position in the electromagnetic induction heating layer 1 of the fixing belt 10. The heat value Q is shown. Here, the heating area H is defined as an area where the heating value is Q / e or more, where Q is the maximum heating value. This is an area where a heat value required for fixing can be obtained.

The temperature of the fixing nip N is controlled so that a predetermined temperature is maintained by controlling the current supply to the exciting coil 18 by a temperature control system including a temperature detecting means (not shown). . Reference numeral 26 denotes a temperature sensor such as a thermistor for detecting the temperature of the fixing belt 10. In this example, the temperature sensor 26 detects the temperature of the fixing belt 10 based on the temperature information of the fixing belt 10 measured by the temperature sensor 26 before the fixing nip N. The temperature is controlled. This is because the amount of heat applied to the recording material P and the toner t is controlled by controlling the temperature of the fixing belt 10 before the nip.

Thus, the driving roller 31 is driven to rotate,
As a result, the fixing belt 10 rotates, and power is supplied from the excitation circuit 27 to the excitation coil 18 to generate electromagnetic induction heat of the fixing belt 10 as described above, so that the fixing nip portion N rises to a predetermined temperature to control the temperature. In this state, the recording material P, on which the unfixed toner image t has been formed, conveyed from the image forming means is preheated before reaching the fixing nip N.

The recording material P is introduced between the fixing belt 10 and the pressure roller 30 in the fixing nip portion N with the image surface facing upward, that is, opposed to the fixing belt surface, and the image surface is fixed in the fixing nip portion N. The fixing nip N is conveyed together with the fixing belt 10 in close contact with the outer surface of the belt 10. In the process in which the recording material P is nipped and conveyed through the fixing nip portion N together with the fixing belt 10, the unfixed toner image t on the recording material P is heated by the electromagnetic induction heat of the fixing belt 10. The recording material P is heated and fixed on the recording material P. Since the plane contacting the pressure roller 30 at the contact point between the pressure roller 30 and the fixing belt 10 is configured to be parallel to the fixing belt 10, the recording material P contacts the fixing nip N while maintaining the state of contact with the fixing belt 10. enter.

Since the recording material P and the unfixed toner image t are preheated as described above, the recording material P
Even in the case of a sheet, a sufficient heat-fixing time can be obtained. When the recording material P passes through the fixing nip portion N, it is separated from the outer surface of the rotary fixing belt 10 and discharged and conveyed.
After passing through the fixing nip, the heat-fixed toner image on the recording material is cooled and becomes a permanent fixed image.

In this example, since the toner containing a low-softening substance was used in the toner t, the fixing device was not provided with an oil application mechanism for preventing offset, but the toner not containing the low-softening substance was used. In this case, an oil application mechanism may be provided. Also, when a toner containing a low softening substance is used, oil application or cooling separation may be performed.

Hereinafter, each component will be described in detail.

A) Excitation Coil 18 The excitation coil 18 uses a bundle (bundled wire) of a plurality of copper thin wires, each of which is individually insulated and coated, as a conductive wire (electric wire) constituting a coil (wire loop). Are wound several times to form the exciting coil. In this example, the exciting coil 18 is formed by winding 10 turns.

As the insulating coating, a coating having heat resistance is preferably used in consideration of heat conduction due to heat generation of the fixing belt 10.
For example, a coating of amide imide or polyimide may be used. The excitation coil 18 may improve the density by applying pressure from the outside. The shape of the exciting coil 18 is shown in FIG.
As described above, the fixing belt 10 follows the curved surface of the fixing belt 10.
In this embodiment, the distance between the heating layer 1 (see FIG. 8) of the fixing belt 10 and the exciting coil 18 is set to be approximately 2 mm.

As the material of the excitation coil holding member 19, a material having excellent insulation properties and good heat resistance is preferable. For example, a phenol resin, a fluorine resin, a polyimide resin, a polyamide resin, a polyamideimide resin, a PEEK resin, a PES resin, a PPS resin, a PFA resin, a PTFE resin, a FEP resin, an LCP resin, or the like may be selected.

Magnetic cores 17a and 17b and exciting coil 1
8 and the heat generating layer 1 of the fixing belt 10 are closer to each other as much as possible, the magnetic flux absorption efficiency is higher. However, if this distance exceeds 5 mm, the magnetic flux absorption efficiency is remarkably reduced. It is better to be within. Also, 5mm
Within the range, the heating layer of the fixing belt 10 and the exciting coil 1
The distance of 8 need not be constant.

Excitation coil holding member 19 of excitation coil 18
About the lead lines 18a and 18b (see FIG. 5) from
Insulation coating is applied to portions outside the excitation coil holding member 19 outside the bundled wires.

B) Fixing Belt 10 FIG. 8 is a schematic diagram of the layer structure of the fixing belt 10 in this embodiment. The fixing belt 10 of the present embodiment has a heating layer 1 made of a metal belt or the like which is a base layer of the fixing belt 10 of electromagnetic induction heat generation.
And an elastic layer 2 laminated on its outer surface and a release layer 3 laminated on its outer surface. A primer layer (not shown) may be provided between each layer for adhesion between the heat generating layer 1 and the elastic layer 2 and adhesion between the elastic layer 2 and the release layer 3.
In the fixing belt 10 having a substantially cylindrical shape, the heat generating layer 1 is on the inner surface side, and the release layer 3 is on the outer surface side.

As described above, when the alternating magnetic flux acts on the heat generating layer 1, an eddy current is generated in the heat generating layer 1 to generate heat.
The heat of the heat generating layer 1 heats the fixing belt 10 via the elastic layer 2 and the release layer 3, and heats a recording material P as a heating material passed through the fixing nip N to form a toner image. Heat fixing is performed.

A. Heating Layer 1 The heating layer 1 is preferably made of a ferromagnetic metal such as nickel, iron, ferromagnetic SUS, and nickel-cobalt alloy. A non-magnetic metal may be used, but a metal such as nickel, iron, magnetic stainless steel, or a cobalt-nickel alloy, which has good magnetic flux absorption, is more preferable.

It is preferable that the thickness is larger than the skin depth represented by the following formula and 200 μm or less. The skin depth σ [m] is expressed as σ = 503 × (ρ / fμ) ^1/2 with the frequency f [Hz], the magnetic permeability μ, and the specific resistance ρ [Ωm] of the excitation circuit 27.

FIG. 10 shows the depth of absorption of electromagnetic waves used in electromagnetic induction. At a depth deeper than this, the intensity of the electromagnetic waves is 1 / e or less. It has been absorbed.

The thickness of the heat generating layer 1 is preferably 1 to 100 μm.
m is good. If the thickness of the heat generating layer 1 is smaller than 1 μm, most of the electromagnetic energy cannot be absorbed, and the efficiency becomes poor. On the other hand, if the heating layer 1 has a thickness of more than 100 μm, the rigidity becomes too high, and the flexibility deteriorates, which is not practical for use as a rotating body. Therefore, the thickness of the heating layer 1 is 1 to
100 μm is preferred.

B. Elastic Layer 2 The elastic layer 2 is made of silicone rubber, fluorine rubber, fluorosilicone rubber, or the like, and has good heat resistance and good thermal conductivity. The thickness of the elastic layer 2 is preferably from 10 to 500 μm.
The elastic layer 2 has a thickness necessary to guarantee the quality of a fixed image.

When a color image is printed, a solid image is formed over a large area on the recording material P, especially for a photographic image. In this case, if the heating surface (release layer 3) cannot follow the unevenness of the recording material or the unevenness of the toner layer, uneven heating will occur, and uneven gloss will occur in the image in portions where the amount of heat transfer is large and small. Areas with a large amount of heat transfer have high gloss,
The glossiness is low in portions where the amount of heat transfer is small.

When the thickness of the elastic layer 2 is 10 μm or less, the unevenness of the recording material or the toner layer cannot be completely followed, and image gloss unevenness occurs. Also, if the elastic layer 2 is 1000
If it is more than μm, the thermal resistance of the elastic layer becomes large, and it is difficult to realize quick start. More preferably, the thickness of the elastic layer 2 is preferably 50 to 500 μm.

If the hardness of the elastic layer 2 is too high, the elasticity of the elastic layer 2 cannot follow the irregularities of the recording material P or the toner layer, resulting in uneven image gloss. Therefore, the hardness of the elastic layer 2 is not more than 60 ° (JIS-A), more preferably 45 °.
(JIS-A) The following is preferred.

The thermal conductivity λ of the elastic layer 2 is from 6 × 10 ⁻⁴ to 2 × 10 ⁻³ [cal / cm · sec · de].
g] is good.

The thermal conductivity λ is 6 × 10 ⁻⁴ [cal / cm ·
[sec · deg], the thermal resistance is large, and the temperature rise in the surface layer (release layer 3) of the fixing belt becomes slow. Thermal conductivity λ is 2 × 10 ⁻³ [cal / cm · s
ec · deg], the hardness becomes too high or the compression set becomes worse.

Therefore, the thermal conductivity λ is 6 × 10 ⁻⁴ to 2 × 10
^-3 [cal / cm · sec · deg] is preferable. More preferably, 8 × 10 ^{−4 to} 1.5 × 10 ⁻³ [cal / cm · s
ec. deg].

C. 2. Release layer The release layer 3 is made of fluororesin, silicone resin, fluorosilicone rubber, fluororubber,
A material having good releasability and heat resistance, such as silicone rubber, PFA, PTFE, and FEP, can be selected.

The thickness of the release layer 3 is preferably 1 to 100 μm. If the thickness of the release layer 3 is less than 1 μm, there arises a problem that uneven coating of the coating film causes a part having poor releasability or insufficient durability. On the other hand, if the thickness of the release layer exceeds 100 μm, there is a problem that heat conduction is deteriorated. In particular, in the case of a resin-based release layer, the hardness becomes too high, and the effect of the elastic layer 2 is lost.

As shown in FIG. 9, in the configuration of the fixing belt 10, the heat generating layer 1 on the side of the belt guide surface (the heat generating layer 1).
The heat insulating layer 4 may be provided on the side opposite to the elastic layer 2).
As the heat insulating layer 4, a fluororesin, a polyimide resin, a polyamide resin, a polyamideimide resin, a PEEK resin, P
ES resin, PPS resin, PFA resin, PTFE resin, F
A heat-resistant resin such as an EP resin is preferable.

The heat insulating layer 4 has a thickness of 10 to 10
00 μm is preferred. When the thickness of the heat insulating layer 4 is smaller than 10 μm, the heat insulating effect cannot be obtained, and the durability is insufficient. On the other hand, if it exceeds 1000 μm, the magnetic core 17
The distance from the a.17b and the exciting coil 18 to the heat generating layer 1 increases, so that the magnetic flux is not sufficiently absorbed by the heat generating layer 1.

The heat insulating layer 4 can insulate heat generated in the heat generating layer 1 so as not to go to the inside of the fixing belt 10.
The heat supply efficiency to the recording material P side is improved as compared with the case where the heat insulating layer 4 is not provided. Therefore, power consumption can be suppressed.

C) Temperature Detection In this example, as shown in FIG. 2, in order to cut off the power supply to the exciting coil 18 at the time of runaway, the temperature is set at a position facing the heat generating area H (see FIG. 6) of the fixing belt 10. A thermo switch 50 as a detection element is provided.

FIG. 7 is a circuit diagram of the safety circuit used in this example. Thermo switch 50 which is a temperature detecting element is +24
The VDC power supply and the relay switch 51 are connected in series.
1 is cut off, the relay switch 51 operates,
When the power supply to the excitation circuit 27 is cut off, the power supply to the excitation coil 18 is cut off.

The thermoswitch 50 sets the 0FF operating temperature to 2
The temperature was set at 20 ° C. Further, the thermoswitch 50 is disposed in a non-contact manner on the outer surface of the fixing belt 10 so as to face the heat generating area H of the fixing belt 10. Thermoswitch 50 and fixing belt 1
The distance between 0 and 2 was approximately 2 mm. Thus, the fixing belt 10 is not damaged by the contact of the thermoswitch 50, and the deterioration of the fixed image due to durability can be prevented.

According to this embodiment, when the fixing device goes out of control due to a device failure, unlike the configuration in which heat is generated at the fixing nip N as shown in FIG. Even when the power is supplied to the coil 18 and the fixing belt 10 continues to generate heat, the paper is not directly heated because no heat is generated in the fixing nip portion N where the paper is sandwiched. In addition, since the thermo switch 50 is provided in the heat generation region H where the heat generation amount is large, the thermo switch 50
When the thermo switch 50 is turned off by sensing 0 ° C,
The power supply to the exciting coil 18 is cut off by the relay switch 51. Therefore, since the firing temperature of the paper is around 400 ° C., the heat generation of the fixing belt can be stopped without firing the paper. A temperature fuse may be used as the temperature detection element in addition to the thermoswitch.

(Second Embodiment) In this embodiment, as shown in FIG. 11, an auxiliary roller 2 is provided upstream of the fixing nip.
This is a configuration in which 0 is added. In the present example, the transfer material P is
Since the fixing belt 10 is suppressed by the added auxiliary roller 20, preheating by the fixing belt 10 can be efficiently performed.

If the fixing belt 10 is separated from the transfer material P during the preheating, the toner image is blurred.
This problem can be prevented by bringing the transfer material P into close contact with the fixing belt 10 with the auxiliary roller 20 as in this example. FIG. 11 shows an example in which one auxiliary roller 20 is provided. However, a plurality of auxiliary rollers 20 may be provided, or an auxiliary belt 21 may be used instead of the auxiliary roller as shown in FIG.

(Other Embodiments) 1) The fixing belt 10 of heat generation by electromagnetic induction is used for heating and fixing a monochrome or one-pass multi-color image.
The elastic layer 2 may be omitted. The heat generating layer 1 may be formed by mixing a metal filler into a resin. The heating layer may be a single layer member.

2) The pressing member 30 is not limited to the roller body, but may be another type of member such as a rotating belt type. Further, in order to supply thermal energy to the recording material also from the pressing member 30 side, a heat generating means such as electromagnetic induction heating is provided on the pressing member 30 side so as to heat and control the temperature to a predetermined temperature. You can also.

3) The heating device of the present invention is not limited to the image heating and fixing device of the embodiment, but may be an image heating device for heating a recording material carrying an image to improve the surface properties such as gloss, and an image heating device to be supposedly applied. It can be widely used as a means / apparatus for heat-treating a material to be heated, such as a device for heating and drying a material to be heated, a heating laminating device, and the like.

[0100]

As described above, according to the present invention,
Since the pre-heating is performed in the process of transporting the recording material to the nip section, even in the case of thick paper or OHT, a longer heating and fixing time than usual is required to obtain a predetermined glossiness and light transmittance. do not do. As a result, there is an effect that it is possible to obtain a heating device that performs an appropriate heating process without reducing the number of printed sheets per minute.

Further, by applying this heating device, the unfixed toner formed on the recording material by the image forming process can be reliably heated and fixed on the recording material, and a high quality image can be formed. There is an effect that an image heating device and an image forming device can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram illustrating an image forming apparatus of the present invention.

FIG. 2 is a schematic cross-sectional side view of a main part of a heating device according to a first embodiment applied to the image forming apparatus.

FIG. 3 is a front model view of a main part of the heating device.

FIG. 4 is a schematic cross-sectional front view of a main part of the heating device.

FIG. 5 is a diagram showing a relationship between a magnetic field generating means and an excitation circuit.

FIG. 6 is a diagram showing a relationship between a magnetic field generating means and a heating value Q.

FIG. 7 is a circuit diagram showing a safety circuit.

FIG. 8 is a schematic diagram of a layer configuration of a fixing belt having an electromagnetic induction heat generation property.

FIG. 9 is a schematic diagram of a layer configuration of a fixing belt having electromagnetic induction heat generation.

FIG. 10 is a graph showing the relationship between the depth of a heating layer and the intensity of electromagnetic waves.

FIG. 11 is a schematic cross-sectional side view of a main part of a heating device according to a second embodiment.

FIG. 12 is a cross-sectional side view of a heating device according to a modification of the heating device of FIG. 11;

FIG. 13 is a schematic cross-sectional side view of a conventional heating device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Heat generation layer 2 Elastic layer 3 Release layer 4 Heat insulation layer 10 Fixing belt 16 Belt guide 17 Magnetic core 18 Exciting coil 19 Exciting coil holding member 20 Auxiliary roller 21 Auxiliary belt 23a / 23b Flange member for regulating / holding end of fixing belt Reference Signs List 26 Temperature detecting element (thermistor) 30 Pressure roller as pressing member 31 Drive roller 50 Safety temperature detecting element

Claims (9)

[Claims] 1. An electromagnetic induction heating member for generating electromagnetic induction under the action of a magnetic field generated by a magnetic field generating means, and a rotatable first nip formed by pressing against the electromagnetic induction heating member to form a nip portion. A heating device for heating the member to be heated passing through the nip portion by the heat generated by the electromagnetic induction heat generating member, wherein the electromagnetic induction heat generation member is an endless belt, inside the endless belt. A second pressure member rotatable at a position facing the first pressure member, and a plane contacting the second pressure member at a contact point between the second pressure member and the endless belt; The heating device is configured to be parallel to the endless belt. 2. The heating device according to claim 1, wherein said magnetic field generating means is disposed inside an endless belt. 3. The heating apparatus according to claim 2, further comprising means for bringing the heated member into contact with the endless belt at an upstream side of the nip portion in the traveling direction of the heated member. 4. The heating apparatus according to claim 1, wherein said magnetic field generating means is provided on an upstream side of the nip portion in a traveling direction of the member to be heated. 5. The endless belt according to claim 1, wherein the temperature detecting means of the endless belt is provided on the endless belt downstream of the magnetic field generating means and upstream of the nip portion.
A heating device as described. 6. A rotatable second inner side of the endless belt.
A member for rotatably holding an end of an endless belt is provided at an end of the pressing member.
A heating device as described. 7. The endless belt has a width of L _B ,
The pressing length of the pressure member L _R1 of, when a contactable length of the endless belt of the second pressure member and L _R2, satisfying the relationship L _B> L _R1> L _R2 The heating device according to claim 1, wherein: 8. An image forming means for forming an image on a recording material, and a heating device according to any one of claims 1 to 7, wherein the image forming means forms an image on the recording material. An image heating device, wherein the formed image is subjected to a heat treatment by the heating device. 9. An image forming means for forming an image on a recording material, and a heating device according to any one of claims 1 to 7, wherein the image forming means comprises: An image forming apparatus comprising: the heating device as an image heating device that heats an image formed on the recording material.